Fig. 5. Diagram showing the unidirectional influxes of Na⁺ across isolated posterior gills of C. granulatus in the absence (white column) and presence (grey column) of 0.1 mmol l^-1 acetazolamide (AZ). Analysis of the two groups by paired Student's t-test revealed that the difference was significant at P=0.0007. See Materials and methods for details.